Doctor Silas Mills watched from a promontory near the Southern edge of Palmer Land as the last boat docked at Shackleton Port, disgorging its crates. Adjusting his CO2 filtration mask so he could speak clearly, he turned to his family and handed out three small envelopes, one to each of them.

“Keep these safe,” he said, “I’ll let you know when.”

His wife, Tricia, folded hers into the pocket of her raincoat and looked at him with desperate eyes.

“How long?” She reached out an arm to pull her eldest daughter close.

“I don’t know,” he said. “The phytoplankton is all dead. We probably have a few months’ oxygen left. A lot depends on how quickly the seas turn stagnant and start emitting hydrogen sulphide. January maybe.”

“What about the electrolysis project?”